"The bike was in my son's name. But we sold it about four years back, since my son left for the US", he told the police.

Sankaranarayanan, said he was shocked when police knocked his door and told him that the bike had been used in the blast.

Speaking to mediapersons on Thursday, Bangalore Police Commissioner Raghavendra Aurandkar stated that the preliminary lab reports have shown that ammonium nitrate was used.

"However, we are not sure for now about the rest of the contents," he said, adding, "I would not like to comment on who could be behind this attack, but it is a terror strike for sure. Everyone who needs to be questioned will be questioned".

Retired telecom staffer owned bike used in Bengaluru blast

Police sources said that while they were tracking down the number plate of the bike, they were also inquiring whether a fake number plate was used.

Investigations are on with the state police coordinating with their counterparts in Karnataka and the National Investigation Agency, the sources said.

Terror struck Bengaluru on Wednesday ahead of the upcoming Karnataka assembly elections when a low-intensity bomb exploded near the bustling BJP city office in a busy residential area injuring at least 16 people, including 11 policemen.

The bomb, apparently strapped to the motorbike with a Tamil Nadu registration plate parked between a van and a car, went off around 10.30 AM about 100 metres diagonally opposite BJP office in Malleshwaram.